In today's world, vehicles such as aircraft, and increasingly, automobiles, rely upon automated and semi-automated systems to aid in their dynamic control. Such systems often comprise means for determining vehicle static and/or dynamic information including vehicle position, velocity, acceleration, and orientation. These systems may use the acquired vehicle information to control the vehicle as it traverses its desired path and/or may communicate the information to a vehicle controller, which may include a driver or pilot or some other participant, to aid in the control of the vehicle.
A variety of means are currently available for determining a vehicle's position relative to a known reference position, such as that of an orbiting satellite, or of a radar installation, or the like. Further, it should be noted that a vehicle's position, once determined, may be expressed as a translation from the reference position. In addition, the vehicle's position relative to other reference positions (i.e., in terms of other frames of reference) may be determined from such position information so long as the positions of the reference positions (i.e., reference frames) relative to each other are known. This may be accomplished by merely translating the frame of reference from that of the initial reference position to that of the alternative reference position. For example, a vehicle's position may be expressed relative to a geographic reference position (i.e., in terms of a geographic reference frame) once its position relative to a satellite, whose position relative to the earth, has been determined. As a result, the position of a vehicle may be geographically referenced by describing its distance and direction from a known geographic reference position. For example, a vehicle's position on the surface of the earth may be described by its latitude and longitude.
In their initial and still common usage, controllers of vehicles would use maps by correlating the positions of their vehicle to the map frame of reference by comparing visible features proximate their vehicles to features depicted on their maps. With the advent of automated control systems and automated means for determining a vehicle's position, however, the speed and accuracy of this process has been vastly improved. These improvements, and the use of automatic and semi-automatic vehicle control, have been made possible by the geographic referencing of maps. It should be noted that if the position of a vehicle is known relative to a geographic reference, then its position may also be correlated to any geographically referenced map or any other geographically referenced information. Moreover, the vehicle's position may then be determined relative to any other point depicted on the geographically referenced map or to any other feature referenced to the map, and thus to the earth.
Depending on the accuracy required for the particular application, maps have approximated the surface of the earth as a two-dimensional plane (ignoring the curvature of the earth), as a 3-dimensional sphere (ignoring differences in elevation/terrain), and as a 3-dimensional body (accounting for variations in elevation/terrain). To further enhance the utility of earth maps in the current age of automated control, and to accommodate the changes that are continually being made to the infrastructure that may be depicted on the maps, such as airports, roadways, bridges, exchanges and legislated restrictions such as one-way traffic regulations, great efforts have been, and continue to be, undertaken to update and improve the detail and accuracy of maps.
Unfortunately, however, the utility of this information is limited by the accuracy and extent to which features are depicted on a particular map or are otherwise commonly referenced. As a result of the proliferation of Computer Aided Design and/or Drafting (CAD) and other uses of computers to aid in the design and depiction of structures (i.e., buildings, roads, airports and other improvements fixedly located on the earth's landscape), extensive libraries of improvement images (i.e., computer line drawings) are currently available for enhancing the features that may be depicted on maps or otherwise correlated with maps and ultimately with vehicle position information. It should be noted that the term improvement image, as used herein, refers to a drawing (such as, for example, a scale drawing) that depicts an improvement or other structure whose position is reasonably fixed with respect to the earth. Such images are commonly produced or used by computers to depict improvements and/or developments such as buildings, bridges and roads. In addition, sufficient information is typically known, or may easily be acquired, to determine the geographic positions of various features of the improvements that are depicted in the image and thus may be utilized as predetermined reference points.
For example, improvement images have been used extensively to depict airport runway configurations. As a result, a comprehensive supply of improvement images currently exists depicting most of the world's airports. Further, hard copies of drawings that were produced prior to the development of CAD systems and that depict relevant improvements may be easily scanned to generate additional improvement images. In the case of airports, improvement images have been produced to depict airport structures such as runways and taxiways, as well as parking, terminal and gate areas. Although these improvement images are often relatively simple, they offer great utility to pilots for manual control of the aircraft while taxiing on airport ground movement surfaces. The scope of the instant invention, however, should not be construed to be limited to airport facilities. For example, it is contemplated that improvement images such as those archived at the building and zoning departments of most local, state or federal government offices could be employed in accordance with the instant invention.
Improvement images exist in a variety of scales and formats, but are often not sufficiently geographically referenced to facilitate their correlation and/or combination with other available information. Thus, some types of improvement images often lack sufficient specific geographic registration information to enable them to be efficiently correlated, and/or manipulated for correlation, with relevant geographically referenced map images. Further, although their use in conjunction with automated aircraft control systems offers great benefits, many available improvement images are not easily or reliably projected onto computer screens for use by current aircraft navigation systems. Moreover, this lack of sufficient referencing information prevents the improvement images from being reliably or accurately re-oriented (i.e., scaled, rotated, and translated) for combination with other geographically referenced images such as maps depicting all or portions of the earth. As a result, many improvement images cannot easily be used in their current form to determine a vehicle's position relative to a depicted feature. Further, current methods for converting improvement images, such as airport map line drawings, involve laborious and time consuming hand processing that is prone to error.